SEOUL, June 27 (Reuters) - North Korea has successfully conducted an important test aimed at developing missiles carrying multiple warheads, state media KCNA said on Thursday.

The test was carried out on Wednesday using a first-stage engine equipped with a solid-fuel based intermediate and long-range ballistic missile, it said.

The dispatch came a day after South Korea's military said that North Korea launched what appeared to be a hypersonic missile off its east coast but it exploded in midair.

KCNA said the missile succeeded in separating warheads which were accurately guided to three preset targets.

"The purpose was to secure the capability to destroy individual targets using multiple warheads," it said.

South Korea, the United States and Japan condemned the launch as a violation of U.N. Security Council resolutions and a serious threat, and warned against additional provocations in the wake of last week's summit between North Korean leader Kim Jong Un and Russian President Vladimir Putin.

During Putin's first visit to North Korea in 24 years, the two leaders signed a mutual defence pact, which Kim lauded as an alliance, but South Korean President Yoon Suk Yeol called it "anachronistic".

In another dispatch, North Korea's defence minister Kang Sun Nam condemned Ukraine's attack on Crimea with U.S.-supplied ATACMS missiles that killed at least four people and injured 151 as an "inexcusable, heinous act against humanity."

The attack highlighted how Washington has served as a "top-class state sponsor of terrorism," he said, adding that any retaliation from Russia would make "the most justifiable defence."

The U.S. State Department said on Monday Washington provided weapons to Ukraine so it could defend its sovereign territory, including Crimea.

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